Microwave oven apparatus



July 25, 1961 s, c, JOHNSON r 2,993,973

MICROWAVE OVEN APPARATUS Filed April 6. 1959 SAFETY SWITCH INVENTORS STEWART C. JOHNSON WILLARD A. SMITH ATTOREEY United States Patent O 2,993,973 MICROWAVE OVEN APPARATUS Stewart C. Johnson and Willard A. Smith, Mansfield, Ohio, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 6, 1959, Ser. No. 804,389 2 Claims. (Cl. 219-1055) This invention relates to ovens, more particularly to ovens of the type wherein food is cooked by microwave energy, and has for an object to provide improved means for illuminating the interiors of such ovens.

Another object of the invention is to reduce the cost of illuminating means for microwave ovens.

A further object of the invention is to provide a visual indication of the presence of microwave energy in a microwave oven, without added cost.

Yet another object of the invention is to illuminate the interior of a microwave oven and simultaneously provide a visible indication of the presence of microwave energy in the oven.

Heretofore, the interiors of microwave ovens have been illuminated by the provision of an incandescent lamp, located exteriorly of the oven cavity and equipped with the usual socket and wiring. Small holes have been provided in the wall of the oven cavity in the region of the lamp to permit light therefrom to enter the cooking cavity while preventing escape of microwave energy. I

The present invention provides a separate lamp compartment or enclosure, adjacent the oven cavity, containing a lamp of the type which is illuminated in the presence of microwave energy. The wall structure separating the lamp enclosure from the oven cavity is provided with one or more openings for passage of a limited amount of microwave energy from the oven cavity to the lamp to illuminate the latter when the oven is energized, and for passage of light from the lamp to the oven cavity to render visible the food being cooked therein.

With this arrangement, no socket or exterior wiring is necessary for the lamp, and illumination of the lamp constitutes a positive visual indication of the presence of microwave energy in the oven.

The foregoing and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

FIG. 1 is a perspective view of an electronic oven constructed in accordance with the present invention, portions of the structure being broken away to more clearly show the invention;

FIG. 2 is a horizontal sectional view, taken along the line II-II of FIG. 1, looking in the direction indicated by the arrows; and,

FIG. 3 is a fragmentary vertical sectional view of the upper portion of an oven, showing a modified construction.

Referring to FIG. 1 of the drawings, there is shown an electronic oven in which a supporting plate 11, of a material transparent to microwave energy, is disposed horizontally in an opening provided in a countertop 12 or other suitable work surface. A dome-shaped wall structure 13 is adapted to overlie the plate 11 and to define therewith an oven cavity or cooking chamber 14 above the plate. Below the plate is a lower enclosure wall 16 providing a radiating chamber 17 to which microwave energy is directed, from any suitable source, by a conventional wave guide 18. A suitable stirrer 19 is provided within the radiating chamber 17 to effect adequate distribution of the microwaves within the radiating chamber, it being understood that these waves pass freely through the supporting plate 11 to the oven cavity 14 thereabove containing the food to be cooked.

A horizontally disposed partition 21 closes the upper end of the dome 13, the latter terminating in a tubular neck 22 by which the dome is connected to suitable mechanism (not shown) for raising and lowering the dome relative to the countertop 12. When the dome is in the lowered position shown, the oven is in position for cooking operation, and when the dome is raised to an overhead position, the countertop is unencumbered for ready placement or removal of food to or from the supporting plate 11, and for normal use of the countertop as part of the work area.

The lower edge of the dome 13 is provided with a horizontal flange 23 adapted, in the operative position of the dome, to be received in a mating recess 24 provided in.

the countertop, the vertical shoulder provided by the outer edge of the recess serving to prevent escape of stray microwaves from the oven cavity. When the dome 13 is seated in the recess 24, the flange 23 will engage a safety switch 26, and as soon as the dome is raised from the recess, the switch will be disengaged, thereby inter" rupting the circuit to the microwave source.

The structure described above in somewhat general.

terms is more fully disclosed in copending application Serial No. 782,101, filed December 22, 1958 by Kenneth L. Woodman, now Patent Number 2,956,144, for Ovens, and assigned to the assignee of this application. For a more detailed description and discussion of the general structure and mode of operation of a microwave oven of this type, reference may be had to the above identified Woodman application.

The present invention includes a horizontally disposed partition 27 in the upper portion of the dome 13, separating the interior thereof into the cooking cavity 14, previously mentioned, and a lamp compartment or enclosure 28, thereabove. A lamp 29 is used within the enclosure 28 and is supported therein by suitable means, such as the spring clips 31 attached to the partition 27. This lamp 29 is of a type which is illuminated in the presence of microwave energy. One such type of lamp is the wellknown fluorescent gas tube lamp which in its normal use today is energized from an electric current source. However, such lamps can be energized without any external source of electric current if they are subjected to a limited quantity of microwave energy, such as is utilized in microwave cooking. However, if such a lamp is submitted to the amount of microwave energy normally present in a microwave oven cavity, the lamp would soon burn out and be rendered useless. Accordingly, it is necessary to restrict the amount of microwave energy to which such a lamp is exposed. Such necessary restriction is effected in the present invention by providing the separate enclosure 28 for the lamp 29, to which enclosure a limited amount of microwave energy is admitted, as hereinafter explained. The partition 27 may be provided in the form of a removable wall, so that the lamp 29 may be replaced in the event it becomes defective for any reason. To this end, the partition is held in place by a plurality of spring clips 32 which engage the lower edge of a flange which depends from the partition.

Preferably, the partition 27 is provided with a plurality of openings 33 for the passage therethrough of a limited amount of microwave energy from the oven compartment 14 to the lamp enclosure 28 to effect illumination of the lamp. The openings 33 perform the further function of providing for passage of light rays from the illuminated lamp to the interior of the oven cavity 14 so that food cooking therein can be readily observed. In this connection, the dome 13 is provided with a pattern of perforations 34 which, while large enough to permit viewing of the interior of the oven cavity, at the same time are of insufiicient size to permit escape of microwaves therethrough. In order that the lighted or unlighted condition of the lamp 29 may be readily observed by the user, the Wall structure defining the lamp enclosure 28 may likewise be provided with a pluralit'yof perforations or openings 36, which permit the lamp to be observed from exteriorly of the lamp enclosure.

The modification of the invention, shown in FIG. 3, difiers from that of FIGS. 1 and 2 in that the openings 33 in the partition 27, for passage of a restricted amount of microwave energy to the lamp 29, may be omitted, and a metallic probe 37 relied upon to conduct a limited amount of microwave energy from the cooking cavity 14 to the lamp to effect illumination of the latter. The probe 37 projects through an opening in the partition 27 and is insulated therefrom by a grommet 37a of suitable non-conductive material. A plurality of small openings or perforations 38 may be provided in the partition 27 for passage of light rays from the lamp 29 to the interior of the cooking cavity 14 to light the interior of the latter.

Since the lamp 29 will be illuminated at all times that microwave energy is present in the oven, the lamp provides a visible signal or indication of the presence of such microwave energy within the oven cavity. This provides, in efiect, an added safety feature in that the user is warned of an active condition of the oven should the same inadvertently exist upon raising of the dome, due to malfunctioning of the safety switch 26. It will be apparent that this added safety feature is obtained without any additional expense whatsoever, since the lamp 29 will be provided as a source of oven illumination, in any event. Furthermore, it will be apparent that this type of lamp will be less expensive than the incandescent type previously'utilized in that no added electrical energy is required, and no external wiring or socket is necessary.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and mod ifications without departing from the spirit thereof.

What is claimed:

1. In a microwave oven, metallic wall structure defining a cooking cavity and an enclosure and including a wall member separating said cooking cavity and said enclosure, means for visually indicating the presence of microwave energy in said cooking cavity and for simultaneously illuminating the latter, said means including a lamp, of the type which is illuminated in the presence of microwave energy, housed in said enclosure, and means for supplying microwave energy to said cooking cavity for cooking food therein, said metallic wall member having one or more openings therethrough for passage, during microwave operation of the oven, of a limited amount of microwave energy from said cooking cavity to said lamp enclosure to energize said lamp and for passage of light from said lamp to said cooking cavity to illuminate the interior of the latter.

2. Structure as specified in claim 1, wherein the metallic wall structure has one or more openings therethrough for rendering visible to an observer, from exteriorly of the oven, an illuminated condition of the lamp.

References Cited in the file of this patent UNITED STATES PATENTS 2,181,889 Hanson Dec. 5, 1939 2,525,624 Stahl et a1. Oct. 10, 1950 2,526,226 Gross Oct. 17, 1950 2,571,156 Nelson Oct. 16, 1951 2,778,911 Valentine Jan. 22, 1957 2,782,292 Long Feb. 19, 1957 2,788,490 Nowogrodzki Apr. 9, 1957 OTHER REFERENCES 'Radio and Television News, June 1951, pages and 61. 

